The frequency response of a pickup coil sensor in an electromagnetic pickup (also known as an induction coil sensor, induction sensor, search coil sensor, pickup coil sensor, or magnetic loop sensor), especially its resonance frequency, is an important determinant of the timbre of amplified sound transferred from vibrating ferromagnetic strings. The resonance frequency is largely a function of the internal resistance, inductance, and self-capacitance of the coil. These properties depend upon the geometry of the coil, the number and density of turns in the winding, and gauge of wire. Heretofore, electromagnetic pickups for stringed musical instruments have comprised one or more coils, each of which is wound with a single strand of wire (referred to as a single-winding coil). The resonance frequency of an electromagnetic guitar pickup, for example, typically lies within the range of 4,000 to greater than 20,000 Hertz. However, the fundamental frequencies of notes on the guitar fret board range from ˜80 Hertz (open sixth string E) to ˜1318 Hertz (first string E at the 24th fret), and the frequencies of the corresponding musically important overtones are mostly less than 4,000 Hertz.
Electromagnetic pickups referred to commonly as ‘single coil’ as disclosed in U.S. Pat. No. 2,087,106 (HART) Jun. 13, 1937 and U.S. Pat. No. 2,089,171 (BEAUCHAMP) Aug. 10, 1937 comprise a single-winding coil (as shown schematically in FIG. 1 and depicted in cross-sectional views in FIG. 10A-10B) in which the winding is disposed about one or more ferromagnetic or permanent magnet pole pieces. Electromagnetic pickups comprising two or more coils (as disclosed in U.S. Pat. No. 2,892,371 (BUTTS) Jun. 30, 1959 and U.S. Pat. No. 2,896,491 (LOVER) Jul. 28, 1959) employ several single-winding coils disposed side-by-side and electrically connected in series or in parallel, often with their magnetic field vectors arranged anti-parallel in order to provide at least partial cancellation of unwanted signal due to external electromagnetic transmissions and main power alternating current. Variations of the two-coil electromagnetic pickup in which one of the single-winding coils is wound with a different gauge of wire (as disclosed in U.S. Pat. No. 4,501,185 (BLUCHER) Feb. 26, 1985) or wound with significantly more turns of wire (commonly referred to as ‘unbalanced’ or ‘ mismatched’ coils) provide for altered timbre of amplified sound due to the coils having different resonance frequencies. Other embodiments of two-coil electromagnetic pickups comprise several single-winding coils that are stacked one atop another (as disclosed in U.S. Pat. No. 3,657,461 (FREEMAN) Apr. 18, 1972) or nested within each other (as disclosed in U.S. Pat. No. 3,711,619 (JONES) Jan. 16, 1973).
Present embodiments provide for the construction of pickup coil sensors comprising a plurality of concurrently wound and fully or partially interpenetrating windings for which the resonance frequency can be varied over a broad range and can be adjusted to emphasize certain frequency regimes. I have found that 1) such coils, whether each winding is used individually or they are connected in series or in parallel, have resonance frequencies that are appreciably different from single-winding pickup coil sensors with the same or similar geometry and similar total number of turns in the winding, and 2) that the frequency response characteristics of such coils can be adjusted by altering the number of turns in each winding, the degree of interpenetration of the windings, and the region within the coil where the interpenetration occurs. In FIG. 17 the frequency response profile for an example of this type of pickup coil sensor is shown for the case in which primary and secondary windings each of ˜2,500 turns of 42 AWG wire are concurrently wound and fully interpenetrating (as shown schematically in FIG. 2 and depicted in cross-sectional views in FIG. 11A-11B) and electrically connected in series 1703 or in parallel 1704. When the primary and secondary windings are connected in parallel a resonance frequency at ˜19,322 Hertz is observed. When the primary and secondary windings are connected in series a resonance frequency at ˜1,363 Hertz is observed. The frequency response profiles for two single-winding pickup coil sensors (as shown schematically in FIG. 1 and depicted in cross-sectional views in FIG. 10A-10B) 1701 with ˜2,500 turns of 42 AWG wire (resonance frequency at ˜17,804 Hertz) and 1702 with ˜5,000 turns of 42 AWG wire (resonance frequency at ˜9,907 Hertz) are also shown in FIG. 17. A pickup coil sensor with concurrently wound and interpenetrating windings can be combined with another such pickup coil sensor or with a single-winding pickup coil sensor to form a two-coil combination with a distinct frequency response profile. In FIG. 18 the frequency response profile for this type of two-coil combination 1803 is shown in which a pickup coil sensor (as shown schematically in FIG. 2 and depicted in cross-sectional views in FIG. 11A-11B) comprising primary and secondary windings each of ˜2,500 turns of 42 AWG wire and in which said windings are connected in series is in turn connected in series with a single-winding pickup coil sensor (as shown schematically in FIG. 1 and depicted in cross-sectional views in FIG. 10A-10B) with ˜5,000 turns of 42 AWG wire. The frequency response profiles for the single-winding pickup coil sensor 1801 and the two wire concurrently wound and interpenetrating pickup coil sensor 1802 comprised by the two-coil combination are also shown in FIG. 18.
The embodiments comprise:    1. A plurality of wires    2. of the same or different gauge    3. that are wound concurrently (in right-handed or left-handed fashion),    4. with or without one or more ferromagnetic pole pieces, magnets, or other material in the core region,    5. with the same or different number of turns,    6. to form fully or partially interpenetrating windings    7. that can be connected in series,    8. in parallel,    9. in phase or out of phase, or    10. connected independently in a circuit or circuits, or    11. not connected in a circuit.
The following is a tabulation of some prior art that presently appears relevant:
TABLE 1Relevant Prior ArtPat. No.Issue DatePatentee8,519,251August 2013Lingel7,288,713October 2007Krozack, et al.7,189,916March 2007Kinman7,022,909April 2007Kinman6,846,981January 2005Devers4,545,278October 2005Gagon, et al.4,501,185Feburary 1985Blucher3,983,778October 1976Bartolini3,715,446Feburary 1973Kosinski3,711,619January 1973Jones, et al.3,657,461April 1972Freeman3,629,483December 1971Welch3,588,311June 1971Zoller3,571,483March 1971Davidson3,541,219November 1970Abair3,535,968October 1970Rickard3,483,303December 1969Warner3,249,677May 1966Burns, et al.3,236,930Feburary 1966Fender3,177,283April 1965Fender3,147,332September 1964Fender3,066,567December 1962Kelley2,911,871November 1959Schultz2,909,092October 1959De Armond, et al.2,896,491July 1959Lover2,892,371June 1959Butts2,683,388July 1954Keller2,612,072September 1952De Armond2,557,754June 1951Morrison2,294,861September 1942Fuller2,293,372August 1942Vasilach2,262,335November 1941Russell2,089,171August 1937Beauchamp2,087,106July 1937Hart